The present invention relates generally to tapping and plugging furnaces that hold and transfer molten material, such as molten metal, and particularly to an arrangement in which large plugs are positioned against and removed from large spout structures of furnaces in a precisely controlled manner.
Molten metal is transferred from a melting furnace to a holding furnace through refractory tap hole structures located in a sidewall of such furnaces at the hearth line, i.e., at the level of the floor of the furnace. The tapping of metal is ordinarily accomplished manually by handling a heavy steel bar, with a steel plug mounted on the end of the bar, which together can weigh 50 pounds or more. Large hammers are used to set the bar in the tap hole when plugging the furnace and to remove it when tapping metal. Such hammering can cause damage to the spout structure of the furnace. Spout structures are made of a refractory material, which material tends to be weak in tensile strength.
A major problem is the weight of the bar and plug assembly and the location of the spout assembly, i.e., plant personnel must hand munipulate the bar into place over a hot trough and often with molten metal moving at high velocity. Burn injuries can occur if proper procedures are not carefully followed.
Over the years, the size of holes for tapping molten metal has increased. Many are now four inches in diameter. The plug and bar assemblies have increased in weight accordingly. Safety considerations currently limit tap hole sizes to about four inches, but larger sizes are needed to decrease metal transfer time and increase production rates.